This invention relates generally to management techniques for a wireless communications network and, more particularly, to a system and method for layering a packet data service in the wireless communications network.
There are many types of calls that are being performed in various telecommunications networks. The public switched telephone network (xe2x80x9cPSTNxe2x80x9d) handles voice calls between two voice terminals and has been adapted to handle data calls between two data terminals through use of modems and the like. Likewise, many data networks, such as the internet, handle data and voice calls between two terminals.
Wireless networks are also commonplace, and can connect to the PSTN through one or more mobile switches. Furthermore, the wireless networks can be connected to a data network through interface systems such as one using data interworking function technology. In this way, a mobile terminal operating in a wireless network can connect to a remote terminal through the wireless network and further through the PSTN or the data network.
For example, in FIG. 1, the reference numeral 10 designates a wireless telecommunications system 10. In the present example, the network 10 is a cellular network or a personal communication service network that utilizes code division multiple access (xe2x80x9cCDMAxe2x80x9d) technology. The CDMA network 10 includes several components, including a mobile switching center (xe2x80x9cMSCxe2x80x9d) 12, a base station controller (xe2x80x9cBSCxe2x80x9d) 14, a home location register (xe2x80x9cHLRxe2x80x9d) 16, and an interworking function system (xe2x80x9cIWFxe2x80x9d) 18. It is understood that the components described in FIG. 1 are merely exemplary, using terms that are well known in the telecommunications industry to represent only one type of component.
The components of the CDMA network 10 are connected in various methods, such as signaling system 7 (xe2x80x9cSS7xe2x80x9d), Ethernet, and so forth. To accommodate the various methods, the interconnections are illustrated in a functional sense. Therefore, it is understood that the descriptions of the components and interconnections therebetween are meant for exemplary purposes.
A first data device 20 is connected through a wireless link 30 to the CDMA network 10 using an IS-99 wireless communications device (not shown). IS-99 is a CDMA Circuit Switched Data Specification that defines how a CDMA mobile terminal establishes a circuit call through a modem pool of the IWF 18. Other wireless communication devices can provide similar functionality, such as an IS-707 device. A second data device 24 is connected to a data network 26. For the sake of further example, the first data device 20 is a laptop computer, the second data device 24 is a desktop computer, and the data network 26 is a packet data network (xe2x80x9cPDNxe2x80x9d).
The HLR 16 provides a database for storing customer profile information such as features, dialing capabilities, and a home serving area identification. In the present example, the home serving area identifies the MSC 12 in which the first data device 20 is located. One example of an MSC is a DMS-MTX MSC manufactured by Northern Telecom Ltd. of Montreal, Canada. The operation of the HLR 16 and the MSC 12, along with other switching centers and databases not shown, is well known and understood in the art.
The IWF 18 provides several functions. For one, it establishes control signal communications with the laptop 20 using a predetermined protocol stack. The protocol stack is commonly used to support various communications in the wireless network 10. The IWF 18 also supports a data connection to the remote data terminal 24. The data connection can either be through the PSTN or through the PDN 26.
The IWF 18 is able to establish a data path to the PDN 26 using a CDMA fast connect, or hybrid data call, connection. The IS-99 wireless terminal 22 of the first data device 20 connects with the BSC 14 through a wireless link 30. The BSC 14 has a link 32 (either wireless or physical) to the MSC 12. The MSC 12 then establishes a data path (e.g. using a data bus) and a signaling path (e.g., using Ethernet), collectively designated with a bus 34, to the IWF 18. The IWF terminates the signaling path with an IS-99 device and routes the data to the data network 26.
The IWF 18 is also able to establish a data path to the PSTN using a CDMA circuit switched connection. With a circuit switched data path, the IWF 18 terminates the signaling path with an IS-99 device and routes the data to an internal modem pool (not shown). The data from the modem pool is then sent back to the MSC 12 on a bus 36 and from there to the PSTN through a trunk 38. Once connected to the PSTN, several different gateways are available to the PDN 26, such as through an internet service provider (also not shown).
CDMA technology, such as is used in the wireless network 10 of FIG. 1, is a continually evolving technology. In 2nd generation CDMA systems, when the data device 20 sends data over the CDMA network 10, the device repeatedly performed the steps of: making a call, sending data, and hanging up. This inefficient use of system resources by making multiple calls is being addressed by a 3rd generation CDMA technology.
Standards for 3rd generation CDMA systems are currently being designed to include a medium access control (xe2x80x9cMACxe2x80x9d) layer for handling layer specific functions. The proposed MAC layer controls access to the physical channels in the CDMA network 10 on which the data device 20 may arrange packets of data.
The MAC layer proposed for 3rd generation systems gets the data device 20 on and off a path or channel without making multiple calls. Instead of using xe2x80x9cslots,xe2x80x9d such as in time division multiple access networks, CDMA technology provides software-based logical channels through which data is sent. These logical channels, each of which may provide a different data service, can simultaneously exist on the same physical channel. The proposed MAC layer also serves to coordinate these different services.
A particular logical channel has transmission and reception characteristics and is restricted to carrying a certain set of information. During system operation, information on a logical channel is carried on a real physical channel, which is a radio channel employing CDMA technology. In this way, a logical channel is said to be mapped to a physical channel.
Logical channels are divided in two broad classes: common and dedicated. Common logical channels are mapped to common physical channels while dedicated logical channels are mapped to dedicated physical channels. A common physical channel is a CDMA based radio channel that may be shared between one base station and a plurality of mobile stations. A dedicated physical channel is a CDMA based radio channel that is assigned by a base station (for a period of time) to exchange information between exactly one base station and exactly one mobile station.
Referring to FIG. 2, the MAC layer proposed for 3rd generation systems attempts to get the data device 20 on and off a path or channel without making multiple calls. The proposed MAC layer operates according to a packet data service state diagram 100. Each state of the state diagram 100 depicts different stages of packet data service and is associated with conditions of the network 10. These conditions include permitted actions and the availability of specific logical channels.
The state diagram 100 for the proposed MAC layer is an enhancement of the 2nd generation packet data service (as described in IS-707) and includes a packet null state 102, an initialization state 104, a reconnect state 106, an active state 108, a control hold state 110, a suspended state 112, and a dormant state 114.
The packet null state 102 is the initial state and corresponds to the absence of packet data service. In the packet null state 102, no dedicated FL (Forward Link, from base station to mobile) or RL (Reverse Link, from mobile to base station) channels are allocated and no packet data service is active. However, the common physical channels packet access channel (PACH) and packet paging channel (PPCH) are both available.
The initialization state 104 corresponds to all the initialization steps of the packet data service including: service option negotiation and connection, traffic channel allocation and initialization, radio link protocol (RLP) initialization, and finally a point to point protocol (PPP) initialization. As in the packet null state 102, only the PACH and PPCH channels are available.
The reconnect state 106 corresponds to the re-establishment of data communications during an established packet data session. The data device 20 (FIG. 1) reaches this state when it is going from a dormant state to an active state. The reconnect state 106 corresponds to all activity necessary to re-establish the data communications channel including: service option negotiation and connection, traffic channel allocation and initialization, and RLP initialization. PPP has already been established and does not require initialization. As in the previous state, only the PACH and PPCH channels are available.
The active state 108 is the most highly connected state with both dedicated FL and RL channels established. In this state, the logical dedicated MAC control channel (DMCH), dedicated signaling control channels (DSCH), and dedicated traffic channels (DTCH) are established. The packet data service 100 stays in this state for the duration of user data transmission and reception.
The control hold state 110 is entered when user data has not been exchanged for a predetermined period of time. Although the logical DTCH channel is dropped, the logical DMCH and DSCH channels are still available. This maintains a dedicated channel between the BSC 14 and data device 20 that allows control information to be exchanged quickly. If user data is to be exchanged, execution returns to the active state 108.
If the packet data service spends a predetermined period of time in the control hold state and still no user data is exchanged, execution proceeds to the suspended state 112. Continuous communication between the BSC 14 and data device 20 cease since all dedicated channels are dropped. Only the common channels PACH and PPCH are present. Although this frees up system capacity, some system resources, such as the service option and RLP, are still logically maintained. The suspended state 112 allows a quicker return to the active state 108 than from the dormant state 114.
After a relatively long period of time with no user data exchange, the packet data service enters the dormant state 114. Similar to the suspended state 112, there are no dedicated channels available. Only the common channels PACH and PPCH are present. In addition, the service option is not connected, and RLP is lost. However, PPP is retained and the packet data session is still logically connected. This allows the return to the active state 108 if the exchange of user data is desired.
In general, the proposed MAC layer 100 begins at the packet null state 102 and execution proceeds to the initialization state 104 upon receipt of a packet service request from the data device 20. Once initialized, a xe2x80x9cservice optionxe2x80x9d is connected and execution proceeds to the control hold state 110. The service option remains connected when in states 108, 110 and 112, and is not connected in the remaining states. Transitions from one state to another occur for many reasons, such as responses to user actions, system events, or the flow of user data.
A problem with the proposed MAC layer 100 is that it is a monolithic packet data model that captures every operational aspect of the packet data service in one application. As a result, the proposed MAC layer 100 is very difficult to modify or add features without impacting the entire model. In addition, certain functionality performed by the MAC layer 100 is redundant with functionality performed by other layers in the CDMA network 10.
The present invention, accordingly, provides a communications system and method that separates operational aspects of a service to be provided on a network into separate, independent state diagrams. To this end, one embodiment provides a method of layering a communication service in a communications network by decomposing the communication service into several different service layers. The method then defines a dynamic behavior of the service layers and an interaction therebetween. Once the behavior and interaction between the layers is defined, the method creates a control element with which to coordinate the service layers.
In one embodiment, the communication service is a packet data service, such as would be used in a CDMA wireless network. The packet data service may work independently of a voice service in the communications network.
Another embodiment provides a method for facilitating a packet data service in a communications network, such as a CDMA wireless network. A first layer is provided for monitoring and controlling the use of logical channels on a physical layer in the CDMA wireless network. A second layer is provided for performing point-to-point protocol (PPP) functions and a third layer is provided between the first and second layers for receiving and coordinating data transfers therebetween. In one embodiment, each of the layers is controlled by its own, independent state machine.
In another embodiment of the above described method, the CDMA wireless network includes a medium access control (MAC) layer that is dependent on the physical layer. This physical layer dependent MAC layer dynamically maps the logical channels to a set of physical channels on the physical layer.
In yet another embodiment of the above-described method, a fourth layer is provided for managing call processing messages and functions in the CDMA network, the fourth layer being controlled by a fourth state machine. The fourth layer may also support radio protocol functions.
Another embodiment provides a method for facilitating a packet data service and a voice service in a CDMA communications network. The method provides a first MAC layer for monitoring and controlling the use of logical channels used by the packet data service, a second MAC layer for monitoring and controlling the use of logical channels used by the voice service, and a third MAC layer for mapping logical channels to physical channels on the physical layer. In some embodiments, there may also be a fourth MAC layer for monitoring and controlling the use of logical channels used by a different data service, such as circuit data.
The method also provides a first set of upper-level layers for performing PPP functions and call control functions for the packet data service and a second set of upper-level layers for performing PPP functions and call control functions for the voice service. The first and second sets of upper-level layers interact with the first and second MAC layers, respectively. Also, the first and second MAC layers and the first and second sets of upper-level layers all operate independently from each other. As a result, multimedia service is coordinated among different, physical layer independent MAC layers and a common, physical layer dependent MAC layer.